The elegant demonstration by Milkovich et al that graft copolymers can be prepared by the copolymerization of macromonomers (hereafter "macromers" for brevity), with conventional small monomers has initiated a spate of publications in this field. Particular interest has been focussed upon the radical polymerizations of vinyl monomers because it was expected that the rate of polymerization and the degree of polymerization on the molecular weight (Mn) of the growing polymer may be substantially the same as that of conventional vinyl monomers. Both the rate and the degree of polymerization are generally quite high for vinyl monomers which are therefore of major economic interest. The realization that a large moiety adjacent the vinyl head group often reduces the rate of polymerization of the macromer because of the relatively low molar concentration of reactive end groups, particularly at high conversions where also the increased viscosity of the reaction mass reduces the diffusion of the macromer to the reaction site, has done nothing to dull this interest.
The particular interest of this invention is to tailor a polyarylene polyether ("PAPE") oligomer which was desired to be not only thermally crosslinkable through its terminal vinyl groups, but was preferably also to be capable of withstanding thermal degradation at a temperature in the range from above 100.degree. C. to about 200.degree. C.
This invention is more particularly related to difunctional polymers of dihydroxybenzene, dihydroxynaphthalene, and diphenols, all referred to herein as dihydric phenols ("DHP"), and the corresponding sulfur (thio) compounds referred to as dihydric thiophenols ("DHTP"), which polymers have a Mn (number average mol wt) less than about 10,000, hence termed oligomers. One or the other DHP and DHTP, or both, are referred to herein as "DH(T)P" for brevity. Such oligomers are defined herein as polymers containing from 2 to about 100 repeating units each having the formula --DH(T)P--R.sup.s --, where R.sup.s represents the residue of a linking group. These oligomers contain at least three phenyl or thiophenyl rings which may have inert substituents, each ring linked to another through an O, Si, C or S atom. Such DHP and DHTP oligomers, also, poly[DH(T)P], or [DH(T)P].sub.n, are terminated at each end (hence "di-terminated") with a phenol ("Ph") or thiophenol ("TPh") group respectively, which group may also have inert substituents. For brevity, "di-(T)Ph-terminated" refers herein to either or both oligomers which are Ph- and TPh-terminated respectively.
Most commonly, an anionic living polymer is reacted with electrophiles containing unsaturated functions. For example, polystyrene, polyisoprene, or styrene-isoprene diblock macromers have been terminated with various polyfunctional groups such as alpha-olefin, vinyl alkyl ether, styryl, acrylate, methacrylate, maleic half ester, or epoxy. Macromers have also been synthesized by Tsuruta by a poly-addition reaction of divinyl compounds (Makromol. Chem. 183 29-45, 1981), and by Hudecek by transformation of reactive polymer end groups (Polym. Bull. 3 143, 1980).
Cationic techniques have also been used for preparing macromers by Kennedy et al (1980) who prepared a polyisobutylene macromer, and by Sierra-Vargas (1980) who prepared a polytetrahydrofuran macromer.
Of more particular interest is that it is known that it is possible to use a wide variety of macromers with one polymerizable vinyl head group, each of which macromers may be tailored in Mn and structural configuration to provide polymers with a wide spectrum of physical properties. Typical of such macromers are those with styryl and acrylate head groups disclosed by Kennedy, J. P. et al in I.U.P.A.C. Intl. Symp. on Macromolecules, Florence, Preprints, p 162 (1980); Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem., 23, No. 2, 99 (1982); Polym. Bull., 6, 135 (1981); inter alia.
In all the foregoing prior art teachings, the macromer was produced in an organic liquid phase in which the reactants were soluble. Styrene has been polymerized and capped with ethylene oxide in a benzene solution, and the polymer in this solution was esterified by reaction with methacryloyl chloride. The mono-terminated material so obtained was a methacrylate-terminated polystyrene macromer which can be polymerized by free radical copolymerization with ethyl acrylate, butyl acrylate, or other suitable monomers. See "Graft Polymers with Macromonomers. I. Synthesis from Methacrylate-Terminated Polystyrene" by Schulz, G. O. and Milkovich, R., J. Appl. Polym. Sci., Vol 27, 4773-86 (1982).
Where the reactants are poorly soluble in commonly available organic solvents, phase transfer catalysis ("PTC") has been used, both in polymer modification (see J M. J. Frechet, Polym. Prepr., 23(1), 139 (1982); and, Y. Imai, J. Macromol. Sci. -Chem., A15, 833 (1981)), and in polymer synthesis (see L. J. Mathias, J. Macromol. Sci. -Chem., A15, 853 (1981); and, F. L. Cook and R. W. Brooker, Polym. Prepr., 23(1), 149 (1982)). In nucleophilic displacement step-growth polymerizations in which PTC syntheses have been used, not only can the need for anhydrous aprotic solvents be obviated but there are also several other advantages. The reaction is very fast, quickly reaching high MW and 100% yield. The polymer weight is relatively independent of the ratio between the nucleophilic and electrophilic reactants. Most importantly, the organic-soluble polymer obtained almost always contains electrophilic species as chain ends, independent of the reaction yield and reactant ratio.
It is known that selected bis(phenols) react with excess chloroethyl vinyl ether ("CEVE") and base in dimethyl sulfoxide ("DMSO") solution; but quite recently, this reaction was more easily accomplished by replacing DMSO with another solvent and employing a PTC, and in particular, 4,4'-isopropylidenediphenol (also, 2,2-bis(4-hydroxyphenyl)propane, or bisphenol A, "BPA") was reacted with CEVE to yield BPA-diethoxy vinyl ether ("DEVE") quickly and in high yield, much greater than 50% (see "Synthesis of Bis(aryloxyethyl) Vinyl Ethers via Phase Transfer-Catalyzed Nucleophilic Displacement in 2-Chloroethyl Vinyl Ether" by R. R. Gallucci and R. C. Going, J. Org. Chem., 1983, 48, 342-346). But BPA-DEVE is not thermally crosslinkable without a cationic catalyst, or free radical catalyst, and has a low glass transition temperature.
In an analogous manner, I have found that a BPA reacts easily with chloromethylstyrene ("ClMS") in the presence of less than about 10 mole percent (mol %), that is, a 0.1 molar equivalent (mol equiv), of a PTC giving excellent yield. The terms "mol %" and "mol equiv" are used herein based on the number of moles of --OH groups in the BPA, or the number of moles of --SH groups in bisthiophenol A ("BTPA"), unless otherwise specified. The acronym "B(T)PA" is used herein to denote either BPA or BTPA. Thus, the option of using a PTC reaction to tailor a BPA bifunctional vinyl-terminated monomer was a second option since the solubility in DMSO, and accomplishing the reaction in the solvent, was not a problem.
Poly(phenylene oxide) ("PPO" for brevity) may be difunctionalized by esterification as is disclosed in "Reactions of Poly(phenylene Oxide)s with Quinones. I. The Quinone-Coupling Reaction Between Low Molecular Weight Poly(2,6-Dimethyl-1,4-phenylene oxide) and 3,3',5,5'-tetramethyl-4,4'-Diphenoquinone", by Dwain M. White, Jour. of Polym. Sci., Polym. Chem. Ed., Vol 19, 1367-1383 (1981).
Unlike prior art syntheses, this invention is directed to different difunctionalized oligomers. These are (A) oligomers of at least one DH(T)P, also referred to as poly[DH(T)P] or [DH(T)P].sub.n, which are formed by a condensation reaction with a reactive linking group resulting in the connection of two DH(T)P moieties with a linking residue R.sup.s ; such oligomers are soluble in organic solvents, and may be esterified in solution in the presence of base; and, (B) alkali metal salts ("bisphenolates") of at least one of the R.sup.s -linked DH(T)P oligomers formed as described, which salts are essentially insoluble at room temperature, or only soluble in the aforementioned solvents at elevated temperatures in the range from about 70.degree. C. to about 150.degree. C., yet may be either esterified or etherified essentially quantitatively. As defined herein, Ph-terminated polyphenylene ("PP") is an oligomer of a dihydricphenol (DHP), namely 1,4-dihydroxybenzene or hydroquinone ("HQ") which may have inert substituents, in which oligomer the backbone includes at least three phenyl rings, one connected to another through an ether O atom; or, PPO oligomers which are R.sup.s -linked.
However, it must be kept in mind that a reaction with ClMS, or other reactant with a thermally polymerizable vinyl group, at a relatively higher temperature than room temperature will result in polymerization of the ClMS and the reaction is therefore unsuitable. It is unnecessary to state that difficulty polymerizable reactants will be of little interest for the purposes of this invention.
Though an .alpha.,.omega.-di(vinylbenzyl)BPA oligomer VB-(BPA).sub.n -VB (the "VB", vinylbenzyl being the residuum of the ClMS, and the BPA representing the residuum of the BPA), is thermally crosslinkable, it is excessively brittle, and of little practical economic interest. It appeared that, if an oligomer with more desirable properties than that of BPA could be tailored to be thermally crosslinkable, it might have an adequately high T.sub.g. By dint of an exhaustive search, a likely such oligomer appeared to be a relatively low Mn oligomer of a known PAPE oligomer which is analogous to the relatively high Mn PAPEs disclosed in U.S. Pat. No. 4,108,837 the disclosure of which is incorporated by reference thereto as if fully set forth herein.
Unfortunately, a reaction with a bisphenolate in solution is difficult because the salt is essentially insoluble at room temperature in commonly available solvents and precipitates. Further, relating to the use of a PTC reaction to functionalize a PAPE under usual base-catalyzed PTC reaction conditions, the precipitated polymer hydrolyzes. This hydrolysis reaction vitiates the benefits sought of an efficient PTC reaction. The problem was to nullify, essentially completely, the damaging side effects of the hydrolysis reaction. The need for a solution to the problem was particularly pressing because, not only is a bisphenolate of a PAPE difficultly soluble in DMSO at room temperature even when the solution is kept anhydrous, but the reaction is also unsatisfactory because of the scatter of products formed with poor yield.
Proof that the hydrolysis problem of a particular PAPE, namely an aromatic polyether sulfone ("APS") oligomer with only one phenol chain end, was solved, was provided in experiments the results of which were published in an article titled "Comb-Like Polymers and Graft Copolymers from Macromers. 1. Synthesis and Characterization of Methacrylate and Styrene Macromers of Aromatic Polyether Sulfones" by Percec, V., Rinaldi, P. L., and Auman, B. C. in Polymer Bulletin, 10 215-222 (1983). The styrene-terminated (St-terminated) macromers are thermally polymerizable but give only soluble comb-like or graft copolymers. We also made a APS-MA in which the APS was terminated at only one end with a methacrylyl ("MA") residuum but it was neither thermally crosslinkable, nor solvent-resistant.
I know of no instance where a sodium or potassium salt or other bisphenolate of a di-Ph-terminated DH(T)P oligomer has been prepared which is substantially insoluble in commonly available organic solvents at room temperature, yet has been used to provide a solution in which the reaction occurs so as to undergo a modified Williamson etherification which results in substantially 100% yield of an oligomer having a vinyl, or more specifically a VB head group at both ends of the oligomer. The process of my invention provides for such a reaction with OH-terminated oligomers of a large variety of polyDH(T)P linked through a number of different R.sup.s. Among these oligomers are (a) aromatic polyether and polythioether sulfones (all referred to as "APS" for brevity) in which the R.sup.s is a diphenyl sulfone (DPS) residue of a dihalophenyl sulfone (DHPS) linking group; (b) PPO oligomers linked with a diphenoquinone linking group, as disclosed in White, supra; and (c) aromatic polyethers and thioethers in which the R.sup.s is not a sulfone. When the DHP is bisphenol A, and the R.sup.s is DPS, the repeating unit is bisphenol A sulfone ("BPAS"); when the DHTP is bisthiophenol A, the repeating unit is bisthiophenol A sulfone ("BTPAS"), both of which sulfones are together referred to herein as `bis(thio)phenol A sulfones`, and for brevity, "B(T)PAS". As a result, salt of a wide spectrum of DH(T)P oligomers with terminal OH or SH groups may be esterified or etherified to contain terminal reactive vinyl, and more specifically VB groups, which VB-containing oligomers may then be thermally polymerized rapidly to yield solvent-resistant materials.
The difunctionalized DH(T)P oligomers may also be used as an intermediate for the synthesis of other compounds. For example, the di(styrenated) oligomer may subsequently be converted to an .alpha.,.omega.-di(ethynylbenzyl) PAPE which has terminal triple bonds known to be desirable for the development of thermally curable matrix resins for lightweight composite materials, without the evolution of volatile by products. (See P. M. Hergenrother, J. Polym. Sci., Polym. Chem. Ed., 20, 3131 (1982).